There are lots of races in various TCP benchmarks on bots recently:

BenchmarkTCP6OneShotTimeout-4       1000        307762 ns/op
==================
WARNING: DATA RACE
Read by main goroutine:
  testing.RunBenchmarks()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/testing/benchmark.go:325 +0xa89
  testing.Main()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/testing/testing.go:443 +0x237
  main.main()
      /var/folders/q5/9m80sxt95q19qcx8r96_vqlr0000gp/T/go-build520565622/net/_test/_testmain.go:331 +0xdc

Previous write by goroutine 35:
  testing.(*common).log()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/testing/testing.go:311 +0x232
  testing.(*common).Logf()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/testing/testing.go:322 +0x7e
  net.func·076()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/tcp_test.go:79 +0x19b
  net.func·081()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/tcp_test.go:141 +0x45c
  runtime.gosched0()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/runtime/proc.c:1417 +0xaf
  net.(*pollDesc).PrepareRead()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/fd_poll_runtime.go:76 +0x4f
  net.(*netFD).Read()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/fd_unix.go:224 +0x10a
  net.(*conn).Read()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/net.go:122 +0x11f
  net.(*TCPConn).Read()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/dial.go:1 +0x74
  net.func·077()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/tcp_test.go:86 +0x9e
  net.func·081()
      /Users/builder/workspace/darwin-amd64-race-cheney-1b80f9a5165b/go/src/pkg/net/tcp_test.go:141 +0x4fa
==================

http://build.golang.org/log/805f04d7d9e103e167e4362449329e5ad6853c81